I'm looking for a reliable way to constrain the "pi zero spy camera" to a pcb. Is soldering back plate of the camera to a large pad a plausible idea? Is it safe to pass the camera through a reflow oven?

A lower-temperature option would be to use fusible interfacing.. basically hot-melt glue in tape form, used in sewing. I use it to tack pieces of copper-clad together all the time. Dry-mount film, used for mounting pictures, is another version of the same thing.

Thank you for your suggestion. Currently looking into the hot melt tapes you mentioned. I also came across the use of jb-weld on pcbs, which looks like it could be an even more permanent solution. In any case, I think I can figure this out now.